In a refrigerating device or an air conditioner of split type that execute refrigerating cycles, generally, refrigerant discharged from a compressor is delivered to a first heat exchanger, the refrigerant condensed in the first heat exchanger is expanded by expansion means, and thereafter the refrigerant is delivered to a second heat exchanger through a first communication pipe (This will be referred to as “a liquid pipe,” as necessary). Then the refrigerant vaporized in the second heat exchanger is returned to the compressor through a second communication pipe (This will be referred to as “a gas pipe” as necessary).
As well-known, among global environmental problems on refrigerating devices and air conditioners of such a type are (1) ozonosphere protection, (2) energy saving, (3) countermeasures against global warming (reduction of emission of CO2 etc), and (4) reuse (recycling) of resources. Especially, in terms of ozonosphere protection among the global environmental problems, R22 (HFC22) which has conventionally been used is not suitable refrigerant since R22 has a high ODP (Ozone Depletion Potential). For alternative refrigerants to R22 having the high ozone depletion potential, there have been listed R410A (having a composition of HFC32:HFC125=50:50 in weight ratio), R407C (having a composition of HFC32:HFC125:HFC134a=23:25:52 in weight ratio), R32 (HFC32) and the like.
As for energy saving, on the other hand, there is a notice that coefficients of performance (COP) of specified air conditioners must be improved by approximately 4 percent by the end of September, 2004 (Notice No. 190 from the Ministry of International Trade and Industry of Japan, based upon “the Law concerning the Rational Use of Energy”). Thus, refrigerant having a large COP value is required to be used from viewpoint of energy saving.
Requirements for prevention of global warming have been getting increasingly stringent. Refrigerating devices and air conditioners are evaluated with use of an index on global warming referred to as TEWI (Total Equivalent Warming Impact). TEWI is represented as the total of an impact of release of refrigerant into the atmosphere (a direct impact) and energy consumption by the device (an indirect impact). The direct impact includes GWP (Global Warming Potential), and the indirect impact includes the inverse of COP. In order to prevent global warming, accordingly, refrigerant having a small GWP value and a large COP value has to be selected so as to decrease TEWI value.
As for above-mentioned GWP, GWP values of R407C and R410A are 1980 and 2340, respectively, and are a little larger than 1900 of R22 GWP value. On the other hand, a GWP value of R32 is 650 and is about one-third of GWP values of R22, R407C, and R410A. That is, R32 having such a small GWP value is extremely effective for prevention of global warming.
As for COP, COP values of R407C and R410A are generally equivalent to COP value of R22, whereas COP value of R32 larger than that of R22 has not been obtained. In other words, actual COP values of R32 that greatly exceed COP of R22 have not been obtained in the refrigerating devices that execute refrigerating cycles with use of R32, though such devices are theoretically expected to have high COP values in view of characteristics of R32. In such a refrigerating device, on the other hand, there occur phenomena such as increase in pressure and discharge temperature relative to those with use of R22. In addition, slightly flammable R32 has a problem of difficulty in establishing a consensus on safety thereof. Therefore, the industrial world has not employed R32 as alternative refrigerant for actual products.
In room air conditioners with refrigerating capacity between 2.2 kW class and 5.0 kW class in which e.g. conventional R22 refrigerant is used, a diameter of liquid pipe is set to 2/8″ as shown by a reference character L01 in FIG. 2, and diameters of gas pipe are set to ⅜″ and 4/8″ as shown by reference characters G01 and G02 in FIG. 3, respectively. Herein, diameters of pipes are represented by nominal diameters on inch system with use of a symbol ″. In packaged air conditioners with refrigerating capacity between 4.5 kW class and 14.0 kW class in which conventional R22 refrigerant is used, diameters of liquid pipe are set to 2/8″ and ⅜″ as shown by reference characters L01 and L02 in FIG. 2, and diameters of gas pipe are set to 4/8″, ⅝″ and 6/8″ as shown by reference characters G02, G03 and G04 in FIG. 3. As apparent from the above figures, diameters of liquid pipe and gas pipe tend to be set larger with increase in refrigerating capacity. This is because the flow rate i.e. velocity of refrigerant increases and thereby pressure loss increases in a pipe having a same diameter.
The larger a diameter of a pipe is, however, the more extensive and the more difficult piping work such as connection of and work on the pipe is. On the other hand, a large number of types of pipe cause a problem of bothersome production control of air conditioners. The same goes for devices in which R410A, R407C or the like is used as refrigerant in place of R22.